(1) Field of the Invention
The invention relates to an imprinting jig for putting a thermoplastic sheet therebetween and an imprinting apparatus. Particularly it relates to the imprinting jig and apparatus used for a thermal imprinting process for transferring or printing a fine pattern onto the thermoplastic sheet by heating and applying pressure.
(2) Related Art
Professor Stephen Y. Chou et al. of, Princeton University have made a number of reports on a nano-imprinting process which prints a fine pattern having a high aspect ratio at a moderate price. The nano-imprinting process includes mainly an optical nano-imprinting process in which ultraviolet curing resin is used for printing a pattern, and a thermal nano-imprinting process in which heat and pressure are applied to a thermoplastic substance to print a pattern. Especially the latter process has been attracting attention since the process can produce flat panel displays, electronic cards and the like at a low cost since a sheet material is used (hereinafter, this process will be referred to as “sheet thermal nano-imprinting process”).
In the field of recording media, attention has been paid to a technique in which an optical disk pattern is transferred onto a thin polycarbonate (PC) sheet such as an optical disk substrate through the sheet thermal nano-imprinting process, and the thin PC sheet is directly used as a recording medium, thereby recording capacity per unit volume is dramatically increased. For example, JP-A-2003-91970 proposes a mass storage record reproduction system configured to combine a thin optical disk having a thickness not greater than 100 μm with a stabilizer for stably rotating the thin optical disk with little run out of its surface.
A substrate of an optical disk is generally produced by injection molding. When the thin substrate as described above is produced by injection molding, however, resin cannot be filled in a gap between a mold and a first die (hereinafter, referred to as “stamper”), since the gap is extremely narrow. Thus, it has been technically difficult to apply the injection molding process to producing a thin substrate. In addition, the technique for patterning a thin substrate by a 2P method is expensive although it is possible to produce the thin substrate. On the contrary, the sheet thermal imprinting process, which directly print a pattern on a thin sheet substrate, is remarkably advantageous technically and in cost in relation to the conventional techniques described above.